Virtual laser operator

ABSTRACT

A laser controller interconnected with an electric discharge laser communicates with a remote computer incorporating a display screen programmably emulating a conventional keyboard. The display screen has a plurality of imaged virtual keys each programmably emulating a physical key of a conventional keyboard. Some virtual keys programmably emulate a prescribed sequence of keystrokes, which control, monitor, and record the laser operation. A prescribed sequence can optionally be automated, conditional, or interrupted by operator prompts. The remote computer communicates serially with the laser controller through an electrically conductive cable, a fiberoptic link, or a wireless channel. A keystroke is typically applied by manually pressing the position of a corresponding virtual key on a touch sensitive screen, or alternatively by actuating a conventional pointing device. The electric discharge laser can be a KrF or ArF excimer laser, or a F 2  molecular laser, which can be applied as a radiation exposure source for microlithography.

FIELD OF THE INVENTION

This invention relates to a control system and operator interface for alaser, and particularly for an electric discharge laser used in anindustrial application.

BACKGROUND

Lasers for industrial applications, such as KrF or ArF electricdischarge lasers for microlithography (see U.S. Pat. No. 4,959,840,issued Sep. 25, 1990 to Akins, et al.), typically incorporate a lasercontroller, resident at the laser. Input and output interfaces to thelaser controller are typically provided in two ways: (i) through anoperator actuated hand held terminal, and/or (ii) through a workstationcontroller that acts as a master controller, with the resident lasercontroller acting as its slave. The workstation controller primarilycontrols and synchronizes workstation subsystems, such as workpiecepositioning and orientation and other process functions relating to thespecific industrial application. The interface specifications betweenthe laser controller and the workstation controller may vary greatly,depending on the application. For example in microlithography,subsystems include the laser, illumination system, projection system,and scanner.

A primary function of the hand held terminal is to operate the laserindependently of the workstation and application. The hand held terminaltypically permits complete operation of the laser by a human operatorand acts as a primary means of communication between the laser and theoperator. For example, all laser status conditions (e.g., operationalstate, operational errors, etc.) are communicated from the residentlaser controller to the operator, usually by visual display, through thehand held terminal. Likewise, the operator can control various functionsof the laser, e.g., changing the operating state, by depressing aprescribed key in the hand held terminal. The keystroke is interpretedby the hand held terminal, translated to an appropriate electricalcommand, and serially communicated to the resident laser controller.

Control of the laser by the operator is greatly enhanced by the abilityto sequence various keystrokes. For example, the operator cansequentially change the operating state of the laser, perform a gasrefill, again change the operating state of the laser, and run the laserby a prescribed sequence of keystrokes. Conversely, the laser controllerkeeps the operator informed of the status of the laser by displayingrelevant information at the hand held terminal.

Frequently, a laser operator is required to perform repetitiveoperations with a laser. For example, when a new laser chamber isinstalled, the operator performs a sequence of gas refills, eachfollowed by operation of the laser under different prescribedconditions. The operator typically repeats these operations until thelaser meets certain performance criteria. Similarly, an operatortypically performs a weekly diagnostic check, filling the laser with aprescribed gas composition, operating the laser under differentprescribed conditions, and check the magnitudes of prescribed laseroperating parameters. Typically these magnitudes are then manuallyrecorded by the operator in a log sheet. In some cases, when a number ofoperations are sequenced, an operator may omit an operation or performan operation out of sequence, thereby obtaining erroneous results.Similarly, an operator may inadvertently record data erroneously in amanual log sheet. In either case, the consistency and accuracy of datais suspect, and the results can have adverse consequences for theperformance of the laser and/or of the application.

It is therefore desirable in the art to provide a method and apparatusthat minimize an operator's repetitious tasks, reduces the probabilityof operator error, and enhances the reliability of recording laseroperating status data.

SUMMARY OF THE INVENTION

A laser controller interconnected with an electric discharge lasercommunicates with a remote computer incorporating a display screenprogrammably emulating a conventional input device (e.g., standardcomputer keyboard, keypad, touchpad). The display screen has a pluralityof imaged virtual keys each programmably emulating a physical key of theconventional input device, and at least one of the virtual keys isprogrammably configured to emulate a predefined sequence of keystrokes.The remote computer is interconnected to the laser controller with anelectrically conductive cable, or alternatively through a fiberopticlink or over a wireless communication channel. The virtual keys caninclude a function key and/or a “LASER OFF” key.

A keystroke is applied by manually pressing the position of acorresponding virtual key on a touch sensitive screen, or alternativelyby actuating a pointing device. In some embodiments of the presentinvention a prescribed sequence is automated, whereas in someembodiments a sequence is conditioned on a measured value or on operatorresponse to a prompt. In a preferred embodiment, a keystroke is appliedat a remote computer, serially communicating signals in response to thekeystroke, to effect an action at an electric discharge laser. Actionscan include measuring, recording, and/or changing values of laserparameters, or sequences including any or all of these functions. Aprescribed sequence is typically defined according to a programmablycreated script that links a desired sequence of operations to apreselected keystroke.

The electric discharge laser can be a KrF or ArF excimer laser, or a F₂molecular laser, which can provide a radiation exposure source formicrolithography.

The present invention is better understood upon consideration of thedetailed description below, in conjunction with the accompanyingdrawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention may be better understood, and its numerousobjects, features, and advantages made apparent to those skilled in theart by referencing the accompanying drawings. For simplicity and ease ofunderstanding, the use of similar reference symbols in differentdrawings indicates similar or identical items.

FIG. 1 is a pictorial representation of a subsection of a display screenof a fully functional remote computer that replicates a keypad portionand a display portion of a conventional hand held terminal;

FIG. 2 is a flow diagram illustrating an example of serial communicationprotocol between a remote computer and a laser controller;

FIG. 3 is a block diagram illustrating an example of a serialcommunication link between a remote computer and a laser controller;

FIG. 4 is a logic flow diagram illustrating the use of a singlekeystroke to read and record data from a laser controller;

FIG. 5 is a logic flow diagram illustrating how a data acquisitionprocedure is triggered by a prescribed event;

FIG. 6 is a logic flow diagram illustrating an example of automaticapplication of a prescribed keystroke sequence; and

FIGS. 7A-7G are pictorial examples of display screen segments associatedwith function keys.

DETAILED DESCRIPTION OF THE EMBODIMENTS

The following is a detailed description of illustrative embodiments ofthe present invention. As these embodiments of the present invention aredescribed with reference to the aforementioned drawings, variousmodifications or adaptations of the methods and or specific structuresdescribed may become apparent. These descriptions and drawings are notto be considered in a limiting sense as it is understood that thepresent invention is in no way limited to the embodiments illustrated.

This invention relates to a control system and operator interface for alaser, and particularly for an electric discharge laser used in anindustrial application. Embodiments of the invention can be used with,e.g., ArF and KrF excimer lasers and F₂ molecular lasers formicrolithography. The present invention provides a method and apparatusthat minimize a laser operator's repetitious tasks. Many sequentialtasks can be combined automatically into a single task activated by asingle keystroke. New automated single keystroke tasks can be defined bybuilding from a sequence of predefined subtasks, each previouslyrequiring individual keystrokes. Data acquisition is automated. Relevantdata is automatically logged electronically during the execution ofselected tasks. Electronic data logging can be automatically triggered,when the laser status reaches a predefined condition. For example, ifthe laser controller detects an error, data logging can automaticallyrecord the magnitudes of selected laser parameters at the moment theerror is detected. These aspects of the invention improve theconsistency of data and reduce human error. Other aspects of theinvention provide expanded graphic display capability for convenientpresentation of laser condition monitoring data. Additionally,electronic storage of data facilitates future analysis.

In some embodiments of the invention, the traditional input device,e.g., a conventional hand held terminal, is upgraded to provide the fullfunctionality typical of a compact laptop computer, familiar in the art.A subsection of a display of a laptop or similar computer remote fromthe laser controller can emulate the conventional hand held terminal.Additionally, this emulation can switch seamlessly to provide afunctionally expanded software program resident in the remote laptop orsimilar computer, that provides automated multitask management ofmultiple sequenced tasks previously requiring multiple individualkeystrokes using a conventional hand held terminal. As permitted bycomputer technology and economics, custom configured computers and/orcomputers having greater functionality and/or compactness can besubstituted for the remote laptop computer.

FIG. 1 is a pictorial representation of a subsection 104 of a displayscreen 102 of a fully functional remote computer 100, for example alaptop computer, that replicates a keypad portion 106 and a displayportion 108 of a conventional hand held terminal (not shown). In theembodiment of FIG. 1, virtual keys 110 displayed as images on displayscreen 102 communicate exactly the same commands to a laser (not shown)as do corresponding physical keys on a conventional hand held terminal.A specific virtual key 110 can be actuated by selection with atraditional computer pointing device, e.g., a mouse, track ball, orgraphics tablet and pen (not shown). Alternatively, a virtual key 110can be actuated by manually pressing its position on a touch sensitivedisplay screen, familiar in the art. A virtual key 110, when actuated,serially communicates the function of the key to a laser controlleradjacent to the laser. Conversely, operating status data, e.g., errormessages, are communicated serially from the laser controller to remotecomputer 100, where they are decoded and displayed on display portion108 of remote computer 100.

The replicated display subsection 104 is implemented by a graphic userinterface (gui) of a computer software program, written for example inconventional LabVIEW and/or Visual C++ programming languages, that caneither stand alone or be incorporated as a subprogram into a largersoftware program. A larger program can, for example, sequence severalkeystrokes, wait for a response from the laser controller for eachkeystroke, and/or store the responses received at each sequentialkeystroke. The larger software program replicating and expanding thefunctions of the conventional hand held terminal is referred to hereinas a “Virtual Laser Operator.” The replicated keypad portion 106 ofdisplay screen 102 is denoted herein as a “Virtual Paddle,” containingvirtual keys 110.

FIG. 2 is a flow diagram illustrating an example of serial communicationprotocol 200 between remote computer 100 and the laser controller. InFIG. 2, a keystroke is detected at Module 202. Module 204 checks for thekeystroke, causing module 206 to issue a false logic level if there isno keystroke, whereupon logic control returns to module 204 to checkagain for a keystroke. If a keystroke is present, then block 206 issuesa true logic level, and transfers logic control to module 208, whichlooks up the hexadecimal code for the keystroke and communicates it tothe laser controller. Logic control is then switched to module 210,which checks to see if additional keystrokes have been detected. If so,logic control is returned to block 204; if not, logic flow is terminatedby END module 212. The interface between the laser controller and thecomputer is universal in that the communication protocol therebetween isindependent of the protocol between the laser controller and theapplications dependent workstation controller.

Typically, communication between the laser controller and remotecomputer 100 utilizes an electrically conductive cable, althoughsuitably high-bandwidth fiber optic data links or wireless channels canalternatively be used. FIG. 3 is a block diagram illustrating an exampleof a serial communication link 300 between remote computer 100 and alaser controller 302. Remote computer 100 is interconnected with anelectronic modulator/demodulator (modem) 304 using an electricallyconductive or fiber optic cable 306. Laser controller 302 is similarlyinterconnected with a similar modem 308 using an electrically conductiveor fiber optic cable 310. Modems 304 and 308 are connected together withan electrically conductive or fiber optic serial cable 312.Alternatively, modems 304 and 308 communicate through wirelesstransmission media 314 (represented by a dashed line in FIG. 3),employing, for example, rf, microwave, or optical transmission. Modems304, 308 and cable 312 or wireless transmission media allow two-waycommunication between remote computer 200 and laser controller 302.

Illustratively, a laser operator desires to record and store themagnitudes of the laser's gas temperature and pressure as a function oftime over a particular interval. Using a conventional hand heldcontroller, an operator is required to manually read the magnitudes ofthese parameters from the hand held terminal display and then record themagnitudes manually, e.g., with ink on paper. Using a computer basedVirtual Laser Operator in accordance with the present invention, thelarger software program causes a single keystroke to emulate themultiple keystrokes required to read the magnitudes of the desired twoparameters and to record them, e.g., in a spreadsheet format, forreadout and/or further processing. FIG. 4 is a logic flow diagram 400illustrating the use of a single keystroke to read and record data froma laser controller. A single keystroke is entered at block 402,generating at block 404 the hexadecimal codes of the multiple keysaccording to a predefined script to retrieve the laser data. Data isread at block 406, and is transferred to block 408, where it is stored,for example in a spreadsheet format. Following this operation, logiccontrol is transferred to END block 410, which terminates the readingand logging of data. A data file 412 created at block 408 is optionallyoutputted on, e.g., a printer or display screen.

FIG. 5 is a logic flow diagram illustrating how a data acquisitionprocedure 500 is triggered by a prescribed event. For example, laser gastemperature can be recorded when the laser requires a gas refill, whichis detected in block 502. In this event, the software program checks forthe refill request at block 504. If no refill request is detected, thenblock 506 returns logic control to block 504 to check again for a refillrequest at 502; if a refill request is detected, then logic control istransferred to block 508, which reads and logs the prescribed laserparameters, e.g., acquires and stores the magnitude of the laser gastemperature at the moment the gas refill request is generated. Afterthis operation, logic control is transferred to block 510, whichdetermines if there are further gas fill requests to be checked; if so,logic control is returned to block 504; if not, logic control istransferred to END block 512, which terminates data acquisitionprocedure 500. Entire procedure 500 can be controlled automaticallyaccording to a predefined script initiated by a single keystroke.

Similarly, upon a specified error condition, appropriate diagnostic datacan be recorded, thereby facilitating trouble shooting. Optionally, aprescribed sequence of actions is initiated automatically by emulatingthe corresponding prescribed sequence of keystrokes. FIG. 6 is a logicflow diagram illustrating an example 600 of automatic application of aprescribed keystroke sequence. A single keystroke entered at block 602initiates an automatic sequence of keystrokes according to a predefinedscript. The hexadecimal codes of these keystrokes are retrieved andtransmitted to laser controller 302, actions are initiated, andmeasurements are made at block 604. Results are then compared withdesired endpoint results at block 606. If desired endpoint results arenot achieved, then logic control is returned to block 604, and theprocess is repeated; if desired endpoint results are detected, thenlogic control is transferred to END block 608, which terminates theprocess. Several common maintenance or trouble shooting procedures canbe preprogrammed and made available to an operator, enablingmultifunctional procedures such as fluorine gas optimization, weeklysystems checks, data logging, etc. to be initiated “virtual hot keys”that are actuated with a single keystroke. Complex procedures requiringa multiplicity of sequential keystrokes can be automated. For example,upon a laser chamber replacement, the new chamber is filled with a freshgas mixture and the laser operated at a prescribed repetition rate for aprescribed number of pulses. This refill procedure is repeatedautomatically until the laser efficiency (relative to laser operatingvoltage) reaches a specified value.

Conventionally, with a hand held terminal, the above steps requireoperator intervention and manual entry of multiple individualkeystrokes. In an embodiment of the invention, multiple keystrokes andlaser parameter measurements are fully automated, whereas workstationcommand of the laser controller remains fully functional. The timerequired to perform operator initiated tasks is reduced significantly,and the consistency and accuracy of data acquisition and recording areenhanced. Additionally, Virtual Laser Operator is programmable to issuea prompt on completion of an operation or subsequence of operations, forexample, “TO CONTINUE, PRESS ANY KEY,” allowing the operator to controlcontinuation or termination of the task sequence, as described below inmore detail.

A control bar 112 in the upper portion of display screen subsection 104as illustrated in FIG. 1 is a main user interface, and displays thestatus of communications and the current operating mode of the VirtualLaser Operator program (e.g., direct Virtual Paddle control or automatedcontrol sequence in process). Control bar 112 also includes a “LASEROFF” virtual hot key 114 to stop the laser and place it in a standbystate, and to interrupt all automated processes that may be running,returning control to the Virtual Paddle. Control bar 112 also includes aRESET virtual hot key 116, which stops all programs and returns controlto Virtual Paddle 106. When virtual hot key 114 or 116, for example, isactuated, then a corresponding hexadecimal code is immediately generatedand issued through serial communication link 300 to laser controller 302(see FIG. 3), where it is decoded and places the laser on standby or onVirtual Paddle control. Additionally, control bar 112 includes an arrayof pull down menus 118 that enable an operator to change defaultsettings, request help, change communication settings, and exit theVirtual Laser Operator program. For example, a pull down menu selectionplaces the Virtual Paddle in a programming mode, allowing an operator orprogrammer to enter program instructions in a conventional programminglanguage, i.e., C++, to create a script that links a desired sequence ofmeasurement, data logging, and/or laser control operations to apreselected keystroke. A preselected task sequence is programmable to beexecuted fully automatically. Alternatively, a preselected task sequencecan be broken into individual operations or subtasks, requiring adesired measurement value, and/or an operator response to a prompt, asdescribed above, before proceeding with a subsequent operation orsubtask.

Virtual Paddle 106 emulates the conventional hand held terminal keypad.Functions included in Virtual Paddle 106 are laser ON/OFF keys 120, 122and other command keys normally actuated manually to operate the laser.Most keys are self explanatory, for example having abbreviated Englishlanguage labels. Function keys F1-F8 can be user programmable in theillustrated embodiment to initiate customized keystroke sequences fordata logging and other repetitive tasks, and typically are notdescriptively labeled. FIGS. 7A-7G are pictorial examples of displayscreen segments associated with function keys F1-F8 respectively.

Function F1 illustratively activates a weekly status report, includingmonitoring certain diagnostics at different laser voltages and energies.This program automatically steps through a prescribed sequence of energyand voltage settings, while automatically recording the desireddiagnostic data. FIG. 7A shows an example of a display screen segmentassociated with function F1. Function F2 illustratively enables fieldoptimization of F₂ fluorine gas mixture and optimization of F₂ fluorinegas injection parameters. FIG. 7B shows an example of a display screensegment associated with function F2. Function F4 illustratively allowsan operator to monitor simultaneously up to 3 parameters or diagnosticsfor out of range conditions, for example by displaying magnitudesgraphically as a function of time on 3 color coded graphs. When any oneof the 3 parameters or diagnostics goes out of an operator definedrange, a list of other diagnostics/parameters is queried and logged.FIG. 7C shows an example of a display screen segment associated withfunction F4. Similarly, function F5 illustratively logs a list ofdiagnostics graphically at operator selectable time intervals. Thediagnostics can be entered manually or can be read from a saved file,which can be optionally refreshed by the operator. FIG. 7D shows anexample of a display screen segment associated with function F5.Function F6 illustratively allows an operator to automatically slew thelaser wavelength, while monitoring a desired diagnostic. FIG. 7E showsan example of a display screen segment associated with function F6.Function F7 illustratively reads a Weekly Status Report data file intospreadsheet format, from which it can then be plotted and analyzed fortrouble shooting. FIG. 7F shows an example of a display screen segmentassociated with function F7. Function F8 illustratively allows anoperator to look up descriptions of selected diagnostics. FIG. 7G showsan example of a display screen segment associated with function F8.

While embodiments of the present invention have been shown anddescribed, changes and modifications to these illustrative embodimentscan be made without departing from the present invention in its broaderaspects. Thus it should be evident that there are other embodiments ofthis invention which, while not expressly described above, are withinthe scope of the present invention. Therefore, it will be understoodthat the appended claims necessarily encompass all such changes andmodifications as fall within the described invention's true scope; andfurther that this scope is not limited merely to the illustrativeembodiments presented to demonstrate that scope.

What is claimed is:
 1. An apparatus comprising: an electric dischargelaser having as a normal operator input device a hand held terminal; alaser controller interconnected with said electric discharge laser; anda computer remote from and communicating with said laser controller,said computer being an upgrade for said hand held terminal, andincorporating a display screen having a plurality of imaged virtualkeys, at least a portion of said virtual keys programmably emulatingphysical keys on said hand held terminal, at least one of said virtualkeys configured to programmably emulate a prescribed sequence ofkeystrokes.
 2. The apparatus of claim 1, wherein said display screenincludes a “LASER OFF” virtual key.
 3. The apparatus of claim 1, whereinsaid computer is interconnected to said laser controller with anelectrically conductive cable.
 4. The apparatus of claim 1, wherein saidelectric discharge laser is selected from the group consisting of KrFand ArF excimer lasers and F₂ molecular lasers.
 5. The apparatus ofclaim 1, wherein said electric discharge laser provides a radiationexposure source for microlithography.
 6. A method of controlling anelectric discharge laser having as an input device a hand held terminalcomprising the steps of: A) replacing a said hand held terminal with aremote computer having a display screen with virtual keys simulatingkeys on said hand held terminal and having at least one virtual keyconfigured to programmably emulate a prescribed sequence of keystrokes;and B) applying a keystroke by actuating a virtual key on said displayscreen, said virtual key programmably emulating a prescribed sequence ofkeystrokes of said hand held terminal, thereby causing said electricdischarge laser to execute a desired sequence of steps.
 7. The method ofclaim 6, wherein said desired sequence of steps comprises measuring avalue of a laser parameter.
 8. The method of claim 6, wherein saiddesired sequence of steps comprises recording a value of a laserparameter.
 9. The method of claim 6, wherein said desired sequence ofsteps comprises changing a value of a laser parameter.
 10. The method ofclaim 6, wherein a portion of said prescribed sequence is automated. 11.The method of claim 6, wherein a portion of said prescribed sequence isconditioned on an action.
 12. The method of claim 6, wherein saidprescribed sequence is defined according to a programmably createdscript.
 13. The method of claim 6, wherein one of said virtual keysemulates a function key.
 14. The method of claim 6, wherein saidapplying said keystroke is performed by manually pressing the positionof a corresponding virtual key on a touch sensitive screen.
 15. Themethod of claim 6, wherein said applying said keystroke is performed byactuating a pointing device.
 16. The method of claim 6, wherein signalsare communicated between said computer and said laser through anelectrically conductive cable.
 17. The method of claim 6, whereinsignals are communicated between said computer and said laser through afiber optic cable.
 18. The method of claim 6, wherein signals arecommunicated between said computer and said laser through a wirelesscommunication channel.
 19. The method of claim 6, wherein said electricdischarge laser is selected from the group consisting of KrF and ArFexcimer lasers and F₂ molecular lasers.
 20. The method of claim 16,wherein said electric discharge laser provides a radiation exposuresource for microlithography.